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Figure 2: Different Eph/ephrin members act in concert to channel migrating MGE-derived neurons towards the cortex. Schematic drawing of a coronal brain slice from the right hemisphere; medial is right; dorsal is top. The MGE gives rise to parvalbumin-(PV-) and somatostatin-(SST-) positive interneurons. They are driven by EphA4 reverse signalling and guided by ephrin-A5, ephrin-A3, and Sema3A/3F forward signalling. The POA gives rise to neuropeptide Y (NPY), vasoactive intestinal protein (VIP) as well as islet 1 (Isl1) positive interneurons that are guided by EphB1/ephrin-B3 signalling preventing the POA-derived cortical interneurons from entering the striatum (Str). The same Eph/ephrin signalling allows the Isl1+ neurons to migrate towards the Str. The MGE gives rise to the deep migratory stream (DMS) and the POA provides neurons for the superficial migratory stream (SMS). Those streams are divided by a bidirectional EphA4 and ephrin-B3 signalling.